Debarking method and apparatus involving alternate high and lowpressure zones



July 16, 1957 c. MAKINSON 2,799,308

DEBARKING METHOD AND APPARATUS INVOLVING ALTERNATE HIGH AND LOW-PRESSURE. ZONES Filed Nov. 16, 1955 if ll United States atent- DEBARKING METHOD AND APPARATUS IN- VOLVING ALTERNATEHIGH AND LOW- PRESSURE ZONES Clifford Makinson, Rosemere, Quebec, Canada, assignor to Terry Machinery Company Limited, St. Laurent, Quebec, Canada, a corporation of Canada.

Application November16, 1955, Serial .No, 547,157

5 Claims. 01. 144-309 The present invention relates to the debarking of pulp logs.

In the preparation of pulpwood for paper making an important essential step is the removal of thebark -prior to the further processing.

As is well known, one of the chief requirements of quality in the production of pulp is ,that'it shall be substantially free from dirt or particles of log or other objectionable material. It is necessary, therefore, that the pulpwood be completely cleaned ofbark before being processed.

For this purpose, many and varied types'of apparatus have been designed, for example, in the form of rotating cylindrical drums wherein the pulpwood sticksare sub- .jected to tumbling or rotating action with the bark being removed by the friction between the moving pieces of the mass and also generally with the addition .of water to assist in loosening the bark from the wood. There are also other types of debarking machines wherein rotating chain links are brought into contact with the logs as they are passed through the machine. These, of course, are more suitable for the debarking of larger logs rather than pulpwood.

There are also designs of debarking apparatus which employ hydraulic pressure. In some-of these, the logs are passed separately through the machine and a jet or jets of high-pressure water, in the order of 1,000 p; s. i. or more, are directed against the log in such a way that thebark is broken up and removed. Apparatus in the form of pressure chambers into which the logs are placed andsubjected-to increased pressures for the purpose of loosening the bark have also been utilized.

All of these prior art apparatus have certain disadvantages. For example, most barking drums must be loaded and unloaded and for efiicient function they are usually not filled to more than half their capacity. A further disadvantage of the removal of bark by tumbling, for example in a drum or the like, is that the ends are subject to being broomed by the impact of the logs against each other. This brooming or fuzzing of the end fibers provides a surface which is more likely to pick up dust or dirt.

The jet type hydraulic barkers are generally constructed so that the logs are passedseparately through the machine. This means that they must be fed in individually. Further, the degree of the hydraulic pressure required (from 800 to 1,500 p. s.- i.) necessitates fairly high horsepower for the operation, anywhere from 800 to 2,500 H. P. in the larger type, while. the smaller hydraulic type requires anywhere from 500 to 75.0;H. P. per machine. The pressure-chamber type debarkeralso must be loaded and the chamber sealed for each debarkmg operation. A

The present invention provides means of quickly and efiiciently debarking pulpwood logs which eliminates the disadvantages of prior-art apparatus mentioned above.

In accordance with applicants method, ,pulpwood logs are fed in acontinuous stream through a series of alterice nate high' and low-pressure zones, the action of which quickly and etficiently loosens and removes the bark from the logs.

Accordingly, the invention comprises a method of debarking pulpwoodlogs which is characterized by conveyinggthe-logs-in a continuous sequence in a confined fluid stream through a series of alternate zones of'alternate high and low fluid-pressure.

More specifically, in accordance with the invention, an enclosed stream is created having a dimension sufficient to accommodate the diameter of the logs and the formation of the stream-confining means is varied at spaced points to alter the fluid pressure of the stream at these points to create alternate zones of high and low fluid-pressure.- Supplementary pressurized fluid streams are introduced at the high-pressure Zones to further increase the pressure of the fluid at that point and fluiddischarge conduits are provided adjacent the low-pressure zones to emphasize the pressure changes.

By way-of an example, an apparatus, by means of which this method may-be carried out, contemplates the use of a' conduit or pipe of suitable dimensions to ac commodate the logs and through which a continuous stream of fluid is circulated. At spaced points the conduitis enlarged and reduced in the form of venturi type divergences and convergences so that the flow of the stream is expedited and variations in pressure created. At each venturi arrangement or high-pressure zone means are provided for supplying supplementary pressurized fluid into the conduit to increase thepressures at these points. At 'the low-pressure zones, which are staggered alternately with the high-pressure zones, means in the form of discharge outlets lead from the conduit so as to provide a meansof dropping the. pressure sharply after the stream has left the high-pressure zones.

As will beappreciated, the number of high and lowpressure zones can be varied, depending on the pressures involved and the type of logs to be debarked.

With this apparatus a regular series of oscillations of high and low pressure are established withinthe conduit defining the fluid stream so that as the log proceeds, it is subjected to a series of pulsations or shocks which alternately squeeze and release the bark and the log so that the bark quickly becomes loosened and freed from contact with the log.

Since the log is conveyed at all times in a fluid stream, the bark and log, even when separated are carried through the apparatus to a discharge position where they will be separated, for example, by a system of screens or perfo rated plates or any other suitable means.

It has been found 011 experiment that pressures much lower than those needed in standard hydraulic debarking apparatus can be utilized to carry out applicants method. For example, pressures in the high-pressure zones can be eliective at about p. s. i., and in the low-pressure zones reduced to atmospheric pressure or about 9 or 10 p. s. i. Greater pressures of course may be utilized if desired and may be preferable in some variations of apparatus utilized to carry out the present method.

In this respect it will be appreciated thatithe apparatus capable of carrying out the present method may be greatly varied with respect to structure, providing the main essentials of a confined fluid stream and some means of applying alternate high and low-pressure action in sequence to the stream is provided.

For example, it is contemplated that a series of aligned and concentrically enclosed venturi type open-ended cones might be used for this purpose with the diflerence in pressure being accomplished by the force of a high-pres sure-conveying stream only. This would mean that the stream would be subjected to alternate converging and diverging baflles within the enclosure so that the pressure and velocity of the stream would vary to provide alternate low and high-pressure zones as described.

Having thus generally described the nature of the invention, particular reference will be made to the acocmpanying drawing, showing by way of illustration "a preferred apparatus by means of which the method of the invention may be carried out, and in which:

Figure 1 is a diagrammatic plan of a continuous stream debarking apparatus in accordance with the invention.

7 Figure 2 is a fragmentary, vertical, transverse sectional view of a portion of the apparatus shown in Figure 1 along the line 22.

Figure 3 is a diagrammatic, vertical, longitudinal, sectional view of the apparatus shown in Figure 1.

As previously described, in accordance with the method of the present invention, the logs are conveyed in a continuous sequence and in a confined fluid stream, through a series of alternate zones of alternate high and low fluid pressure.

With particular reference to Figure 1, an apparatus by means of which this method can be carried out comprises a basin or reservoir to which the logs are initially delivered and from which they are conveyed through a conduit 12 to a discharge bin or platform 14.

In order to provide the alternate zones of high and low pressure, the conduit 12 is formed so as to have axially spaced cylindrical chambers 16 of considerably increased diameter, with intervening low-pressure portions of considerably lesser diameter.

The chambers 16 each have a straight rear wall 17 and a tapering conical front wall 19 which meets the reduced conduit portions 211. A venturi arrangement 18 is positioned within each of the chambers 16 with a conical tapering rear portion 21 secured at its outer periphery to the inner walls of the chamber 16 and a straight cylindrical front portion 22 positioned in concentric alignment with the axis of the conduit 12 and adjustably secured to the reduced portions 21) so that a leading end 23 of the front portion 22 is spaced from the juncture between the tapering front wall 19 of the chamber 16 and the conduit portion 20.

A fluid-inlet conduit 24 leads into each chamber 16 and fluid under pressure is supplied to each conduit 24 through a main fluid-delivery conduit 26. Means, in the form of a pressure pump 28 in the construction illustrated, are provided to supply the fluid under pressure to the main fluid conduit. A discharge outlet conduit 30, controlled by a valve 31, is also connected into each of the second and third chambers 16, and extends between a main fluid-return conduit 32' which leads back to the pressure pump 28.

It should be mentioned, while not shown in detail, that the forward section 22 of the venturi arrangement is in two telescoping parts with the leading end portion 23 adjustably retained in position by a plurality of bolts secured to the front of each chamber 16. This permits the relative spacing between the front end 23 of the yenturi arrangement and the end of the conduit portion 20 to be varied in order to constrict the flow of high-pressure fluid supplied by the conduit 24, and thus provide the desired pressure and acceleration to that portion of the fluid stream supplied by the conduit 24.

With this arrangement, a fluid stream, and logs placed in this stream, flows from the basin 1% through the chambers 16 and reduced-diameter portions 29 to the discharge bin As the stream passes through each venturi arrangement 18 the flow is accelerated and the pressure is reducedin the conduit 22, While the velocity of the additional fluid under pressure supplied by the conduit 24 into the chamber 16 is further accelerated and the pressure sharply reduced as this additional fluid flows through the constriction between the leading end 23 and the conduit 20. The pressure of the stream when passing from the first portion 20 leading from the first chamber 16 to the rear portion of the next chamber 16 is sharply increased, due to the greater diameter of chamber 16, and notwithstanding the discharge through the outlet 30 of that portion of the fluid stream which was supplied by the conduit 24.

Since this arrangement is duplicated along the length of the stream, the logs are subjected to a series or cycle of high and low-pressure shocks which alternately squeeze and release the logs, thus loosening and removing the bark.

The last of the conduit portions 20 leads into the discharge bin 14 where the fluid stream, logs and separated bark are discharged onto an inclined perforated plate or batfle 40. The openings in the baffie 40 are of such a diameter that the fluid and bark will pass easily through, but not large enough to accommodate the diameter of the logs being debarked. The barked logs, therefore, roll off the plate 40 to a suitable conveyor or stock pile, as desired.

The main volume of the conveying fluid and the bark after passing through the plate 40 come into contact with a second inclined and perforated plate or screen 42 which has smaller openings to allow the fluid to pass freely therethrough but retains the bark. The bark, due to the inclination of the plate 42, and by the action of the falling fluid stream will also pass out of the bin 14 to a suitable conveyor storage pit. The main volume of the fluid then passes into a bark-removal tank having a relatively fine screen 52 and from the tank 511 back into the main fluid-return conduit 32 so as to be recirculated for a further passage through the apparatus.

In order to prevent bark from passing into the fluidreturn conduit 32 from the discharge outlets 30 further bark-removal tanks having filtering screens 62 are provided. Each outlet 30 discharges directly into the top of a tank 60 and the fluid is drained from the tanks 60 by conduits 64 leading into the main fluid-return conduit 32.

From the pressure pump 28 the fluid is delivered back to the main fluid-delivery conduit 26 which is provided with a side conduit 27 having a control valve 29 and from which fluid is delivered back into the basin 10.

The basin 10 is preferably provided with conveying guide walls or baflles 11 as shown, which act to guide the logs to the discharge outlet 13 leading directly to the entry portion 15 of the conduit 12. The conduit portion 15, as illustrated, is disposed at a downward angle from the discharge outlet so as to avoid drawing excessive air into the system.

As will be appreciated, the number and relative spacing between the chambers 16 may be varied to suit the requirements of the fluid pressures utilized, size and type of logs to be debarked, and so on. Further, it will be understood that the apparatus shown may be varied within the scope of the invention. For example, the basin 10 might well be merely a guiding inlet in a natural basin of a lake or river and the fluid pumped directly from and back into such natural fluid-supply source. The particular means illustrated for separating fluid, log and bark could also be varied as is well known in the art.

The main requirement is that the logs be conveyed in a continuous confined fluid stream and, while so conveyed, be subjected to alternate variations of fluid pressure so as to loosen and remove the bark as described.

I claim:

1. A method of debarking pulpwood logs comprising feeding said logs in a continuous axially aligned sequence and in a confined fluid stream through a plurality of spaced alternate zones of high and low fluid-pressure and at varying velocity relative to said high and low-pressure zones whereby as said logs proceed they are subject to a series of hydraulic shocks.

2. A log debarking apparatus adapted to convey logs continuously in a fluid stream through a series of alternate high and low fluid-pressure zones, comprising in combination, a main conduit having a log-inlet end and a logdischarge end and a general cross-sectional diameter sufficient to allow passage of said logs therethrough in the direction of their axial length, but insufficient to permit transaxial passage of said logs, a source of fluid under pressure leading into said conduit adjacent said log-inlet end, said conduit having axially "spaced cross-sectional enlargements and reductions adapted to alternately increase and decrease said pressure of said fluid stream as it progresses from said log-inlet end to said log-discharge end thereby to constitute said high and low fluid-pressure zones.

3. A log debarking apparatus, comprising in combination a fluid-containing log-loading station, a log-discharging station, a fluid conduit having a log-entry end and a log-discharge end extending between said loading station and discharge station, .a plurality of open-ended venturi type fluid-accelerating members disposed in axially spaced relationship within said fluid conduit between said log-entry end and said log-discharge end, said venturi members being disposed in axial alignment with each other and said conduit and providing alternate high and lowpressure zones, and a source of fluid under pressure connected into said conduit between said log-entry and discharge ends and being adapted in combination with said venturi members to impart to a stream of fluid passing through said conduit further low-pressure zones, whereby logs conveyed through said conduit from said log-loading station to said log-discharge station are subjected to a series of high and low fluid-pressure shocks so as to loosen and remove their bark.

4. A log debarking apparatus as claimed in claim 3, wherein the diameter of the portions of said conduit intervening each of said venturi members is of a lesser diameter than the portions of said conduit surrounding said venturi members.

5. A log debarking apparatus as claimed in claim 4, wherein said source of fluid under pressure is connected to said conduit at each of said conduit portions surrounding said venturi members.

References Cited in the file of this patent FOREIGN PATENTS 84,110 Norway Aug. 16, 1954 

